Clinical studies We are exploring the role of damage to specific brain areas, including the reward pathways, in the genesis of fatigue, amotivation, and other common, unexplained complaints of military personnel returning from deployment. This study combines intensive neuroimaging with standard and experimental behavioral measures focusing on effort generation. Another study in collaboration with the Naval Medical Research Center and the Walter Reed Army Institute of Research is looking for evidence of behavioral and brain changes in military personnel with occupational exposure to blast. Laboratory studies In a series of experiments, we are using inhibitory transcranial magnetic stimulation to affect activity in the primary motor and dorsolateral profrontal areas, while healthy individuals learn implicit and explicit motor and non-motor information. To date, we have shown that motor cortex inhibition impairs non-motor, as well as motor, implicit learning. This implies that the motor cortex has access to a wider and more general learning network than currently believed. Using functional MRI in conjunction with inhibitory TMS, we have also shown that the deficit in motor learning comes about through subtle shifts in connectivity, rather than a focal, lesion-like, effect at the stimulation site. We are currently completing studies of the effect of prefrontal inhibition on motor and non-motor implicit and explicit learning tasks. We have initiated a study of how the visuo-spatial adaptation to prism goggles shifts visual attention, a previously described phenomenon. The focus is on the change in fMRI resting functional connectivity between the posterior parietal and frontal attentional areas in the two hemispheres. We will also try to produce analogous changes in connectivity and lateralized attention with inhibitory TMS of the posterior parietal area. We will study patients with neglect after stroke with fMRI to see how prism adaptation affects attention and the size and laterality of population visual fields. We will soon start a study looking at changes in targeted functional connectivity and learning after excitatory TMS. In a replication of a landmark study (Wang et al. Science,2104:345) we will measure resting connectivity between the parietal cortex and hippocampus and explicit associative memory after several TMS treatments to the parietal cortex. We will then see whether this technique can be used to enhance prefrontal-caudate connectivity and procedural learning and do a small trial in amnestic traumatic brain injury patients.